Nowadays use of Computational Fluid Dynamics (CFD) is extended in the aeronautical industry. In order to reduce investment in Wind Tunnel Tests simulation is increasingly used in design activities.
CFD discretizes the physical domain into small cells where the Navier-Stokes equations or simplifications of them, for example the Reynolds Averaged Navier-Stokes, are computed. That implies that in order to perform a good computation one needs a good mesh. Mesh quality is usually defined by cell deformation or the growing ratio between cells. Also residuals computed in the equations give a good idea of the quality of the computation.
The meshes mainly used in CFD are of three types: entirely structured, totally unstructured or hybrid, that is a mixture of these two mesh types.
Structured meshes are meshes whose connectivity is regular and fixed by the topology: each inner vertex is incident to a fixed number of cells and each cell is delimited by a fixed number of sides and edges. All nodes inside a structured mesh can be located using indexes (l,j,k), so that connectivity is explicit.
Unstructured meshes have a completely arbitrary connectivity: a vertex of the mesh can belong to any number of cells and each cell can have any number of edges or sides. The topological data therefore have to be permanently stored to explicitly know the neighbours of each node. The memory cost involved by the use of an unstructured mesh can therefore become very rapidly penalizing.
For complex geometries structured meshes are divided in several blocks, creating multiblock-structured-meshes in which the actual geometry is formed by several structured blocks, having structurally ordered meshes inside them.
The location and distribution of blocks in the physical domain, i.e. the mesh topology, play a significant role for achieving a good description of the geometry. The connection between blocks is also important due to the node propagation, as block faces propagate the numbers of nodes between two blocks in contact.
Several constrains are usually applied to mesh topology definitions, such as the following:                The need that the topology must mark the limits of the surfaces.        The need that the topology must take into account the geometrical discontinuities of the surfaces.        The need to use a “C” topology around the surfaces caused by a Boundary Layer (BL) behaviour, which appears in CFD equations and other equations. In reference to an airfoil, a “C” topology is defined as a topology that surrounds the airfoil so that mesh refinement is not propagated upstream the airfoil and is only located downstream.        
When creating a mesh topology subject to one or more constrains, the mesh may include blocks which do no comply with some quality requirements. A typical mesh quality requirement is that the blocks are as close as possible to perfect squares (2D) or cubes (3D).
In the prior art, two basic options are followed to deal with this type of meshes:                Relaxing the constrains that cause the quality problems.        Working with the mesh and proceeding to a careful evaluation of the results obtained.        
These options are not fully satisfactory and the present invention is intended to solve this drawback.